1. Industrial Field of the Invention
The present invention relates to an electro-optical device, such as a liquid crystal device or an EL (electroluminescent) electro-optical device. The present invention also relates a flexible printed wiring board for use in the electro-optical device, and to electronic equipment including the electro-optical device.
2. Description of the Related Art
In recent years, electro-optical devices have been widely used as information display terminals in portable devices, homes, offices, factories, automobiles, and the like. In particular, liquid crystal display devices have characteristics of low profile, low weight, low voltage, and low power consumption. For this reason, liquid crystal devices are the dominant devices of electronic display both now and in the future, and are actively applied to PDA (Personal Digital Assistants) and the like by making use of the low power consumption.
As one example of conventional liquid crystal display devices, FIG. 9 shows a passive-matrix-driven-type liquid crystal display device 1. The liquid crystal display device 1 is basically composed of a liquid crystal display panel 2 and a printed board 3. The liquid crystal display panel 2 and the printed board 3 are electrically connected via first and second flexible printed wiring boards 4 and 5.
The liquid crystal display panel 2 has a pair of glass substrates 6 and 7 that are arranged to oppose each other. A sealing material (not shown) is provided between the glass substrates 6 and 7 so as to surround a display area. Liquid crystal is sealed in a gap formed by the glass substrates 6 and 7 and the sealing material. On a surface of the glass substrate 6 opposing the glass substrate 7 (opposing surface of the glass substrate 6), a plurality of signal electrodes 8 are formed in parallel with each other. On the other hand, on a surface of the glass substrate 7 opposing the glass substrate 6 (opposing surface of the glass substrate 7), a plurality of scanning electrodes 9 are formed in a direction perpendicular to the signal electrodes 8.
At a predetermined side edge portion (lower side edge portion in FIG. 9) of the liquid crystal panel 2, an edge of the glass substrate 6 is set to project sideways (downward in FIG. 9) from an edge of the glass substrate 7. The projected area (area in which the glass substrate 6 does not overlap the glass substrate 7) constitutes a wiring connection area 6A. In addition, at a side edge portion (left side edge portion) of the liquid crystal display panel 2 adjacent to the above-described side edge portion, an edge of the glass substrate 7 is set to project sideways (leftward in FIG. 9) from the edge of the glass substrate 6. The projected area (area in which the glass substrate 7 does not overlap the glass substrate 6) constitutes a wiring connection area 7A. Signal driver IC chips 10 and 11 are mounted by a COG (Chip on Glass)-technique on the wiring connection area 6A of the glass substrate 6. These signal driver IC chips 10 and 11 are connected to output terminals 8A having a plurality of the extended signal electrodes 8 and to input terminals 12 formed on the edge of the wiring connection area 6A. A scanning driver IC chip 13 is COG-mounted on the wiring connection area 7A of the glass substrate 7. The scanning driver IC chip 13 is connected to output terminals 9A having a plurality of the extended scanning electrodes 9 and to input terminals 14 formed on the edge of the wiring connection area 7A.
An output terminal area 4A of the first flexible printed wiring board 4 is connected via an anisotropic conductive film (ACF) so as to be electrically connected to the plurality of input terminals 12 arranged along the long side of the wiring connection area 6A of the glass substrate 6. Similarly, an output terminal area 5A of the second flexible printed wiring board 5 is connected via an anisotropic conductive film so as to be electrically connected to the plurality of input terminals 14 disposed along the long side of the wiring connection area 7A of the glass substrate 7.
An input terminal area 4B of the first flexible printed wiring board 4 is connected to output terminals 15 formed on the printed board 3 via an anisotropic conductive film or a filter. An input terminal area 5B of the second flexible printed wiring board 5 is connected to output terminals 16 formed on the printed board 3 via an anisotropic conductive film or a filter. The printed board 3 has a predetermined wiring formed thereon and various types of electronic parts mounted thereon. The input terminal area 4B of the first flexible printed wiring board 4 and the input terminal area 5B of the second flexible printed wiring board 5 are connected by different portions, which are offset from each other, of the printed board 3.
As an example of the electronic equipment using the liquid crystal display device having the above-described construction, an electronic equipment includes an input unit, such as a keyboard or a 10-button keypad and displays data by a liquid crystal display panel according to input operation to the input unit. In such an electronic equipment, a liquid crystal display panel and a printed board are incorporated into a chassis (panel-accommodating frame). In this case, two flexible printed wiring boards are bent into the device so that the printed board is arranged at the back of the liquid crystal display panel.
In the above-described liquid crystal display device and the electronic equipment using the liquid crystal display device, however, a display area of the liquid crystal display panel may become small and visibility may be deteriorated when the weight and thickness of the device are reduced to pursue portability. In a portable information device, such as a mobile phone or a pocket size personal computer in which portability is very important, a width of a casing or a width of a frame outside the display area has been reduced to the limit.
As shown in FIG. 10, in the liquid crystal display 1 having the above-described construction, the wiring connection area 7A exists in the lateral direction (left side in the figure), and the wiring connection area 7A is required to secure a width x1 for mounting the scanning driver IC chip 13, a predetermined connection margin x2 for connecting the output terminal area 5A of the flexible printed wiring board 5, and a size x3 for separating the scanning driver IC chip 13 and the output terminal area 5A of the flexible printed wiring board 5. For this reason, there is a problem in that the ratio of the display area accounting for the entire surface of the liquid crystal display panel 2 decreases with a decrease in the width of the liquid crystal display panel 2.
The problem caused by the wiring connection area in the liquid crystal display panel is not limited to a case where a liquid crystal display device or an electronic equipment using the liquid crystal display device is reduced in size. That is, even in an electronic equipment including a relatively large liquid crystal display device, it is demanded that a display area in a casing, such as a chassis, for accommodating the display device is enlarged to the fullest extent by reducing a width of a frame outside a display area of the liquid crystal display panel.
Furthermore, in the above-described liquid crystal display device 1, it is necessary to independently join the flexible printed wiring board 4, which is to be connected to a wiring connection area 6A of the glass substrate 6 having the signal driver IC chips 10 and 11 mounted thereon, and the flexible printed wiring board, which is to be connected to the wiring connection area 7A of the glass substrate 7 having the scanning driver IC chip 13 mounted thereon, to the surface and the back of the printed board 3. For this reason, a modular process becomes complicated and lacks convenience. Since the flexible printed wiring boards 4 and 5 are separately connected to the printed board 3, it is undesirable that the output terminals 15 and 16 formed on the printed board 3 are too close to each other. That is, when connecting the flexible printed wiring boards 4 and 5 using a mounting machine, it is necessary to secure a distance in which the flexible printed wiring boards do not interfere with each other. In this way, the use of a plurality of (in this embodiment, two) flexible printed wiring boards is a factor that prevents a reduction in size of the printed board 3.
It would be desired to provide an electro-optical device capable of simplifying a terminal connecting process and enlarging, for example, an occupancy area of a display area.
In addition, it would be desired to provide a highly convenient flexible printed wiring board.
Furthermore, it would be desired to provide an electronic equipment having a simple modular process, and capable of performing, for example, high visibility display using the electro-optical device according to the present invention.
According to the present invention, there is provided a flexible printed wiring board having wiring formed on an insulating flexible board by a predetermined pattern, the flexible printed wiring board comprising:
a board main body;
a branch wiring section branched from the board main body;
a first output terminal area provided on the board main body;
a second output terminal area provided on the branch wiring section; and
an input terminal area;
wherein the first output terminal area is provided on one surface of the board main body;
the second output terminal area is provided on a surface opposite to the surface on which the first output terminal area is provided;
wiring of the input terminal area is provided on one surface of the flexible board;
the wiring of the first and second output terminal areas is continuously connected to the wiring of the input terminal area; and
an arrangement direction of the wiring in the first output terminal area is the same as an arrangement direction of the wiring in the second output terminal area.
According to the flexible printed wiring board of the present invention, for example, the first substrate and the second substrate can be connected by the single flexible printed wiring board. As a result, according to the present invention, since the number of flexible printed wiring board can be decreased, connecting operation can be simplified.
With this construction, for example, when semiconductor devices, such as driver IC chips are mounted on the opposing surfaces of the first substrate and the second substrate, the single flexible printed wiring board can be connected to the opposing surfaces. In addition, it is possible to join the other end of the flexible printed wiring board connected to the semiconductor devices, for example, to a printed board on which various types of electronic elements, such as power IC chips.
A part of the wiring of the input terminal area may preferably be connected to the wiring of either the first or second output terminal areas formed on the surface opposite to the surface on which the input terminal area is formed via through holes. With this construction, the wiring can be formed on both sides of the flexible substrate via the through holes. As a result, the single flexible printed wiring board can take connections to different surfaces, which are opposing each other.
The branch wiring section may extend in substantially an L-shape from the board main body. In addition, an end of the branch wiring section may be located forward from an end of the board main body.
According to the present invention, there is provided an electro-optical device having an electro-optical material layer formed between a first substrate and a second substrate opposing each other, wherein:
the first substrate includes a first wiring connection area which does not overlap the second substrate;
the second substrate includes a second wiring connection area which does not overlap the first substrate;
the first wiring connection area and the second wiring connection area are connected to the flexible printed wiring board according to the present invention;
the first output terminal area of the flexible printed wiring board is connected to the first wiring connection area;
the second output terminal area of the flexible printed wiring board is connected to the second wiring connection area; and
a direction in which the first output terminal area is connected to the first wiring connection area is the same as a direction in which the second output terminal area is connected to the second wiring connection area.
In the electro-optical device according to the present invention, the first and second output terminal areas of the flexible printed wiring board are connected to the first wiring connection area of the first substrate and the second wiring connection area of the second substrate in the same direction. In other words, the flexible printed wiring board may be connected to the two adjacent wiring connection areas of the first and second substrates not in both of the X and Y directions but in one direction of the X direction or the Y direction. Therefore, the electro-optical device of the present invention has a construction in which the two output terminal areas of the flexible printed wiring board are connected to a long side of one wiring connection area and a short side of the other wiring connection area.
With this construction, it is not necessary to arrange an input wiring terminal used for connection with the flexible printed wiring board on the long side of one of the first wiring connection area and the second wiring connection areas. As a result, a connection margin for the flexible printed wiring board is not required on the long side of one of the wiring connection areas, and the projection size (width) of the wiring connection area can be reduced.
According to the electro-optical device of the present invention, by reducing the projection size of one of the wiring connection areas, for example, the ratio of a display area accounting for the whole of the display panel can be increased. By increasing the ratio of the display area in this way, the width of a display frame surrounding a display opening of a casing (chassis) for accommodating the display panel can be narrowed, and display visibility can be improved.
The electro-optical device of the present invention has an advantage of simplifying a terminal connecting process since the flexible printed wiring board is connected from one direction of the display panel.
Furthermore, according to the electro-optical device of the present invention, convenience of the flexible printed wiring board can be improved since the wiring connection areas of the two substrates can be connected using the single flexible printed wiring board. As a result, in the present invention a modular step for incorporating the electro-optical device into the electronic equipment can be simplified.
Furthermore, the electro-optical device of the present invention can take the following various forms.
(a) A semiconductor device is mounted on at least one of, or preferably, both of the first wiring connection area and the second wiring connection areas. The semiconductor device can include a driver IC chip.
(b) The input terminal area of the flexible printed wiring board is connected to a printed board. With this construction, the output terminal areas of the flexible printed wiring board that are integrally connected to the first and second output terminal areas can be connected to the printed board at one place. For this reason, connecting of the printed board and the flexible printed wiring board is simplified. In addition, the size of the printed board can be reduced since the flexible printed wiring board can be connected to the printed board at one place as described above.
(c) Signal wiring is provided in the first output terminal area, and scanning wiring is provided in the second output terminal area. With this construction, the ratio of the display area accounting for the whole of the display panel can be increased in a passive-matrix-driven-type liquid crystal display device and an EL display device in which the scanning electrodes and the signal electrodes intersect each other, or in an active-matrix-driven-type liquid crystal display device including TFD (Thin Film Diode) elements for each of pixels.
(d) At least one of the first and second substrates is transparent to display light, and at least one of the scanning electrodes and the signal electrodes transparent to the display light are formed on the transparent substrate. With this construction, the ratio of the display area accounting for the whole of the display panel of a reflective display device and a transmissive display device can be increased.
(e) The electro-optical material layer may preferably be a liquid crystal layer. With this construction, assembly convenience of the electro-optical device in a portable information terminal can be increased, and an increase in the ratio of the display area can improve display visibility.
The electronic equipment of the present invention includes the electro-optical device according to the present invention.
The electronic equipment includes, for example, the electro-optical device of the present invention and an input unit for inputting a signal to a driving system of the electro-optical device, and a display panel is accommodated in a casing and the casing is formed with an opening for exposing the whole display area of the display panel. With this construction, the ratio of the area of the opening of the casing can be increased, and a width of a frame surrounding a display unit can be narrowed. For this reason, even if the size of the electronic equipment is reduced, a reduction of the display area can be restricted, and the advantage of improving display visibility is provided.